Support structure for vehicles, made from hollow steel sections

ABSTRACT

The invention relates to a support structure for vehicles, made from a longitudinal member ( 1 ) comprising at least two interconnected hollow sections ( 10, 11 ). One of the hollow sections continues in the direction of the bumper ( 5 ). In the case of a crash with low-speed impact, there is a targeted deformation of the single hollow section ( 10   c ), which makes it possible to carry out repairs economically. In the case of a higher-speed impact, the more rigid support structure of the double hollow section for protecting passengers comes into play. Since in this design the impact absorber, which is usually arranged between the longitudinal member and the bumper, can be done without, there is also a reduction in the number of components required, and thus in the overall weight.

BACKGROUND OF THE INVENTION

The invention relates to a support structure for vehicles, made fromhollow steel sections, comprising a longitudinal member made from atleast two hollow sections which are interconnected in parallel, whereinsaid hollow sections, in front of the support structure of the passengercompartment, bifurcate into a first hollow section supported by thelateral sill, and a second hollow section supported by other parts ofthe support structure.

Various designs of support structures of this type are known. U.S. Pat.No. 4,986,597 describes a design made from extruded aluminium sectionscomprising a longitudinal member which comprises two hollow sections,wherein the hollow sections reach both into the sill region and into theA-pillar of the support structure of the passenger compartment. A secondstructural member reaches from the A-pillar to the sill region so thatoverall, the longitudinal member, the A-pillar and the sill comprise adesign featuring a double structural member. With such a design, afavourable force progression within a support structure is achievedwithout the need for separate gusset structures. There is a disadvantagein that there is a strong deflection to the A-pillar of the longitudinalforces experienced in the case of a crash. Moreover, aluminium extrusiontechnology cannot be used for steel materials in motor vehicleconstruction so that the findings cannot be transferred to steelconstructions.

In another similar support structure (GB-A-529,631), but the hollowsections of which are composed of half-shell shaped profiles, a singlelongitudinal member branches in the direction of the passengercompartment into a first hollow section going over into the lateral sillof the passenger compartment and into a second hollow section supportedon other parts of the support structure. Therefor starting from thebranching point the longitudinal member is extending as a single hollowmember in the direction of the bumper. For this reason in the case of acrash the longitudinal member will be deformed over its whole length upto the branching point. No means are provided for a stepwise reductionof the impact energy.

EP 0 749892 B1 describes a method for producing structural members of asupport structure of vehicles, which structural members with the use ofinterior high-pressure metal forming technology comprise at least twohollow sections which in some regions are hollow sections that areinterconnected in a positive-locking way.

Depending on the locally occurring load, the longitudinal member of thissupport structure comprises the hollow sections which are interconnectedin a positive-locking way, as described above, or comprises a singlehollow section. The structural members can be made from steel or lightmetal. Interior high-pressure metal forming technology implies materialdoubling at the connection surfaces of the hollow sections which areinterconnected in a positive-locking way, so that the design is heavy ifsteel materials are used. The printed publication does not deal with theforce progression in the support structure in the case of a crash.

DE 4208700 C2 describes a lateral sill which comprises two hollowsections of rectangular cross section, which sill, in the direction ofthe front of the vehicle, bifurcates into an engine compartment brace,positioned across the direction of travel, and into a bulkhead memberwhich also extends across the direction of travel.

A lateral frame, arranged at the height of the engine compartment, issupported by the engine compartment brace and the bulkhead crossmember.In the case of a load in longitudinal direction of the vehicle as aresult of a crash, said lateral frame ensures a lead-in of forces bydeflecting the longitudinal forces to the lateral sill. Materials otherthan aluminium can be used. This design, too, is associated with thedisadvantage of being heavy, in particular if steel materials are used,since among other things doubling of materials has to be accepted in theregion of the lateral sill.

Finally, WO 92/11159 describes a rear panel of a vehicle body comprisingtwo crossmembers, wherein each of the ends of the lower crossmember,which are bent in longitudinal direction of the vehicle, is connected toan impact absorber which forms the rear end of a longitudinal member.Apparently this is a longitudinal member which comprises a single hollowsection.

Consequently, the crash energy introduced into the longitudinal memberduring impact from the rear is evenly absorbed along the entire lengthof the longitudinal member or transferred to the passenger compartmentsince no additional strengtheners of the design are provided to protectsaid passenger compartment.

It is thus the object of the present invention to provide a supportstructure for vehicles, of the type mentioned in the introduction, whichsupport structure, with the use of high-strength steel materials with alight overall weight and a small number of components, provides improvedcrash behaviour.

SUMMARY OF THE INVENTION

This object is met by a support structure of the type mentioned in theintroduction in that exactly only one of the at least two hollowsections of the longitudinal member continues in the shape of a singlehollow section in the direction of the bumper. As a result of continuingthe longitudinal member in the direction of the bumper, there is no needfor an impact absorber which would otherwise commonly be used since ithas become an integral part of the longitudinal member. At the face ofis single hollow section, the longitudinal member can be directlyconnected to the bumper by way of a flange, an arrangement which reducesthe number of components required and thus also the overall weight. Acrash with low-speed impact results in targeted deformation of thesingle hollow section, which as part of the repair process can beexchanged in an economical way. in the case of a higher-speed impact,the more rigit part of the longitudinal member with its hollow sectionsthat are connected to form a multi-chamber section to protect passengerscomes into play.

According to one embodiment of the invention, the second hollow sectionof the longitudinal member is supported by the tunnel reinforcement ofthe support structure of the passenger compartment. Thus, the veryconsiderable forces which occur during a crash are deflected to thesupport structure of the passenger compartment of the vehicle in thedesired favourable way. Since, in addition, a strong force deflection,for example to a vertically arranged member, is avoided, and thesections support each other, the danger of deformation of the supportstructure in the case of a crash is reduced.

A further embodiment of the invention provides for the parallel hollowsections to be integrally interconnected. This can be the result ofapplying a welding method wherein the application of a line seam, e.g.by means of laser beam welding, has been shown to be particularlyadvantageous. Welding takes place across the entire length of thelongitudinal member. Furthermore, an advantageous embodiment of theinvention provides for the weld seam to be a stepped weld seam. Thisthus makes possible flexible adaptation of the welding process to themanufacturing-technology requirements of the subsequent user.

For the purpose of reducing weight, material doubling between the twohollow sections of the longitudinal member which forms a multi-chambersection can be avoided in that the two hollow sections share a commondividing wall. From a design point of view this can be realised in thatone of the two hollow sections, at the side facing the other hollowsection, is clipped prior to the joining process, or in that instead ofa closed hollow section, a U-section is used, to which a closed hollowsection is joined only a short distance before the longitudinal memberbifurcates. The use of a clipped hollow section or a U-section makes itpossible to reduce weight while at the same time maintaining practicallythe same rigidity and support structure. Furthermore, a reduction inweight is achieved because it is no longer necessary to reinforce thelateral sills and the A-pillar.

The invention makes it possible to use various profile cross-sections,with polygonal, in particular rectangular, cross-sections beingpreferred. Depending on the lateral or vertical offset of thelongitudinal member relative to the lateral sill and to the tunnelreinforcement of the passenger compartment, the hollow sections arearranged on top of each other or beside each other. If polygonalcross-sections are used, a transverse arrangement is also possible. Ithas been shown to be particularly advantageous if the hollow sections ofa longitudinal member comprise different cross-sections.

This makes for a still more flexible adaptation to the designspecifications of the user. Furthermore, in this way the resistancemoment of the longitudinal member can be precisely set with a view tothe desired crash characteristics of the support structure.

A resistance moment of the longitudinal member, which resistance momentgradually increases in the direction of the passenger compartment,results in increasing rigidity of the support structure in thisdirection. In the case of a crash, depending on the impact speed, thismakes it possible to provide safe protection of the passengers and tominimise the subsequent repair costs. This can be implemented in threeways:

-   -   1. The cross-section of at least one of the hollow sections of        the longitudinal member increases in the direction of the        passenger compartment. The use of a conically-shaped hollow        section is suited to achieving this effect.    -   2. The materials thickness of at least one of the hollow        sections of the longitudinal member increases in the direction        of the passenger compartment.    -   3. In at least one of the hollow sections, the quality of the        steel used increases in the direction of the passenger        compartment.

From the point of view of manufacturing technology, an increase in thematerials thickness and quality of the steel can be realised by the useof tailored blanks for producing one or both hollow sections.

Finally, a particularly advantageous embodiment of the inventionprovides for at least one of the hollow sections to be made from aflexibly rolled sheet. In this way, a progressive change in materialsstrength can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

Below, the invention is explained in more detail with reference to adrawing which shows one embodiment, as follows:

FIG. 1 a diagrammatic top view of a support structure for vehicles,comprising two longitudinal members, arranged one beside the other, andconnected to the lateral sill and tunnel reinforcement of a passengercompartment;

FIG. 2 a perspective view of part of the support structure of FIG. 1,namely a longitudinal member with connected lateral sills and tunnelreinforcement which are connected via sections that bifurcate;

FIG. 3 a perspective view of the longitudinal member according to FIG.2, without sections that bifurcate, with a single continuing hollowsection and a bumper installed at its face;

FIGS. 4 a, b the longitudinal member according to FIG. 2 in lateral viewwith continuous weld seam and stepped weld seam;

FIG. 5 a lateral view of a longitudinal member in the shape of aU-section;

FIG. 6 a cross-section, along the line I-I in FIG. 5, of thelongitudinal member according to FIG. 5

FIG. 7 a cross-section, along the line II-II in FIG. 5, of thelongitudinal member according to FIG. 5

FIG. 8 a-e cross-sections of longitudinal members according to FIG. 2,made from identical hollow sections with weld seams;

FIG. 9 a-c cross-sections of longitudinal members according to FIG. 2,made from different hollow sections with weld seams;

FIG. 10 a longitudinal member comprising a profile cross-section whichprogressively increases in the direction of the passenger compartment;

FIG. 11 a cross-section, along the line III-III in FIG. 10, of thelongitudinal member according to FIG. 10; and

FIG. 12 a cross-section, along the line IV-IV in FIG. 10, of thelongitudinal member according to FIG. 10.

FIG. 13 A top view of the support structure further defining thepassenger compartment.

DETAILED DESCRIPTION OF THE INVENTION

The support structure of a vehicle, which support structure isdiagrammatically shown in partial top view in FIG. 1, comprises twolongitudinal members 1 of the front or rear part of a vehicle, a tunnelreinforcement 2 and two lateral sills 3 of the passenger compartment.The longitudinal members 1 are supported by the tunnel reinforcement 2and the lateral sills 3 by way of bifurcating curved sections 10 b, 11b, made of hollow sections 10, 11. In the design according to theinvention, in the case of a crash, the tunnel reinforcement 2 is alsoused for deflecting longitudinal forces, which results in distributionof the forces to these three components of the support structure whichextend in longitudinal direction of the vehicle in the region of thepassenger compartment, and which results in partial load relief of thelateral sills.

As shown in the perspective view of FIG. 2, the longitudinal member 1comprises two hollow sections 10, 11, one arranged on top of the other.These hollow sections 10, 11 comprise straight sections 10 a, 11 a whichin the direction of the passenger compartments bifurcate into the twocurved sections 10 b, 11 b. At the face ends, these sections 10 b, 11 bare connected to the tunnel reinforcement 2 and a lateral sill 3 of thesupport structure of the passenger compartment.

As also shown in the perspective view in FIG. 3, only the hollow section10 comprises a section 10 c which continues in the direction of thebumper 5, wherein said continuous section 10 c at the face is connectedto a flange 5 a of the bumper 5, which flange 5 a is arranged inlongitudinal direction of the vehicle. The single section 10 c of thehollow section 10 can thus replace the impact absorber.

In their parallel sections 10 a, 11 a, both sides of the hollow sectionsare connected to a multi-chamber section 12 by means of weld seams 4. Asshown in FIGS. 4 a and 4 b, a continuous weld seam 4 (FIG. 4 a) or astepped weld seam 4 (FIG. 4 b) can be provided.

FIGS. 5 to 7 show the use of a U-section 11 e instead of a closed hollowsection along almost the entire length of the multi-chamber section 12.The U-section 11 e is replaced by a closed hollow section 11 d only ashort distance before the bifurcation of the hollow sections 10, 11. Theconnection between the U-section 11 e and the hollow section 11 d isrealised by a further weld seam 4 a.

As shown in FIGS. 8 a to 8 e, longitudinal members can be composed ofhollow sections of various cross-sectional geometries, with the aim ofaccommodating them in a spatially optimal way. By means of thelongitudinal members shown in cross-section in FIGS. 9 a to 9 c, whichlongitudinal members are composed of various hollow sections, theflexibility of the spatial arrangement of the longitudinal member canadditionally be increased.

In the longitudinal member shown in FIG. 10, the hollow section 11comprises a profile cross-section which gradually increases in thedirection of the passenger compartment. Consequently, the resistancemoment of the longitudinal member 1 gradually increases in thisdirection, which results in the desired favourable crash characteristicsof the support structure. FIGS. 11 and 12 show the cross-section of themulti-chamber section 12 at the end of the multi-chamber section whichfaces away from the passenger compartment (FIG. 11), as well as directlyat the point of bifurcation of the hollow sections (FIG. 12).

1. A support structure for vehicles, made from steel sections,comprising a longitudinal member made from at least two hollow sectionswhich are interconnected in parallel, wherein said hollow sections, in afront of the support structure of a passenger compartment, bifurcateinto a first hollow section supported by a lateral sill of the supportstructure of the passenger compartment, and a second hollow sectionsupported by other parts of the support structure of the passengercompartment, wherein only one of the at least two hollow sections of thelongitudinal member continues in the shape of a single hollow section inthe direction of a bumper.
 2. The support structure according to claim1, wherein the second hollow section is supported by a tunnelreinforcement of the support structure.
 3. The support structureaccording to claim 1, wherein the hollow sections are integrallyinterconnected in longitudinal direction.
 4. The support structureaccording to claim 3, wherein the integral connection is achieved bymeans of a weld seam.
 5. The support structure according to claim 4,wherein the weld seam is a stepped weld seam.
 6. The support structureaccording to claim 4, wherein one of the two hollow sections, in theregion of the weld seam, is partially designed as a U-section.
 7. Thesupport structure according to claim 1, wherein the hollow sectionscomprise a polygonal cross-section, wherein the two hollow sections restagainst each other on a flat side.
 8. The support structure according toclaim 1, wherein the longitudinal member is comprised of hollow sectionsof different cross-sections.
 9. The support structure according to claim1, wherein the cross-section of at least one of the hollow sectionschanges in longitudinal direction.
 10. The support structure accordingto claim 1, wherein at least one of the hollow sections is made from atailored blank.
 11. The support structure according to claim 9, whereinthe hollow sections comprise various steel grades.
 12. The supportstructure according to claim 9, wherein the materials of the hollowsections vary.
 13. The support structure according to claim 1, whereinat least one of the hollow sections is made from a flexibly rolledsheet.